In the lighting industry there has for many years been lighting fixtures with a high ingress protection, rated for being used outdoor, for either permanent fixed installations, or for short-term use. With conventional light sources there is traditionally a high amount of heat coming from the discharge light source, and this causes the fixture to be at a constantly high working-temperature, so this usually does not cause a big problem with moisture in the air in the lamp, as the constant high temperature causes the moisture to evaporate into the air, and stay that way, with the high temperature inside the fixture.
In LED based lighting fixtures, things are a bit different. LED based lighting fixtures have a much lower working temperature, and also this temperature is not constant. This is due to the nature of not having a constantly running discharge light source, and the higher efficacy of LED light sources compared to normal light sources.
This causes the temperature of a LED based lighting fixture to vary a lot, and this gives condensation problems inside the fixture. The air from when the unit is assembled is trapped inside the unit, and causes the moisture inside the lighting fixture to sometimes be evaporated into the air, when the temperature is high, and when the temperature inside the fixture falls then the water will condense into dew which sits on PCBs and other parts inside the lamp.
This method describes a way of using an electrolysis-type dehumidifier to prevent this from happening.